Rodent-preventive hinged gangplank



Aug W, 1956 VALEN'HNE EJ57 397 RODENT-PREVENTIVE HINGED GANGPLANK FiledNov. 7. 1952 2 Sheets-Sheet l INVENTOR m-mwmm W. I WALEWWWE ATTORNEY 91956 H. R. VALENTINE RODENT-PREVENTIVE; HINGED GANGPLANK F. Sheets-SheetL2 Filed NOV. '7, 1952 WW NW %N .0 O QM m b m w W T J T- Q) M W U Adv wmH INVENTOR ATTORNEY United States Patent 2,757,397 RODENT-PREVENTIVEHINGED GANGPLANK Howard R. Valentine, Honolulu, Territory of HawaiiApplication November 7, 1952, Serial No. 319,446 6 Claims. c1. 14-71(Granted under Title 35, U. s. Code 1952 see. 266) The inventiondescribed herein may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepay ment of any royalties thereon or therefor.

The invention relates to gangplanks as used for marine and air crafts tofacilitate access to or ingress and egress from such craft, and moreparticularly to that type of gangplank having a pivoted or swingingstairway.

The primary object of this invention is to provide a gangplank of thetype and for the purpose above mentioned which will effectively serve toprevent rodents, primarily rats, from gaining ingress to the craft bysuch gangplank and to this extent may be used to advantage in combatingbacteriological warfare.

Another important object of the invention is to provide a novel coactingplatform and pivoted stairway combination having associated therewith asimple andeifective operating means whereby the stairway is depressibleunder the weight of the user and automatically returns to elevatedposition when relieved of such weight, or the stairway may be secured inthe lowered ordepressed position, optionally, to the end that thestairway can be left in a normally lowered position when the gangplankis being constantly used and canbe kept in a floatingly elevatedposition during periods of sporadic use, thus constituting under suchlatter conditions an effective guard to preclude the entrance of rodentsonto-the craft via the stairway, and consequently preventing the loss,damage, pestilence attributable to suchrodents.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood whenthe following detailed description thereof is read with reference to theaccompanying drawings, in whichis illustrated what is presentlyconsidered a preferred embodiment of the invention and wherein:

Fig. 1 is a side elevational view of a gangplank embodying the featuresof the present invention, with the stairway thereof shown by full linesin depressed or lowered position, and by dotted lines in elevated orguard position;

Fig. 2 is a top plan view of the assembly shown in Fig. l;

Figs. 3 and 4 are fragmentary detail sectional-elevational views takensubstantially on the lines 3--3 and 4-4 respectively of Fig. 2; and

Fig. 5 is a fragmentary horizontal sectional view substantially on theline 5-5 of Fig. 4.

Referring now more in detail to the drawings, wherein like referencecharacters designate like or similar parts, it will be seen that inaccordance with this invention the gangplank comprises generally asupporting structure 6 upon which is mounted a platform 10 and to whichis pivotally connected as at 19,.by apertured lugs 21, a stairwayindicated generally by the reference numeral 20.

Preferably the supporting structure 6 is of skeleton form constructionwas to be light enough in weight to facilitate movability thereof andwhich at the same time taken ice will be of suitable strength for thepurpose designated. It is also necessary that the supporting structurehave no horizontal supports or other appurtenances upon which a rodentcan leap that are closer than five feet to the ground since it has beenfound that rats can leap to that height. To this end the supportingstructure 6 comprises base rails 7, corner posts 3 rising from the baserails 7, cross members 9 bracing the corner posts and also serving tosupport a platform 10, and hand or safety side rails 12 bridging thecorner posts 8 at opposite sides of the structure as clearly shown inFigs. 1 and 2. It will of course be understood that the supportingstructure 6 may be equipped with casters, wheels, or movability of thegangplank. The stairway 20 comprises a plurality of steps 22 and a pairof side walls greater than the spacing of safety side rails 12 to enablesaid walls to freely pass said rails when the stairway is elevated. Thetop edges of side walls 23 form an outset continuation of safety siderails 12 and are usable as hand rails. The steps 22 at the upper endthereof terminate inwardly from the corresponding ends of the side walls23 and effect a continuation of platform 10.

The stairway 20 being hinged as at 19, by apertured lugs 21, to thesupporting structure 6 forms part of the gangplank and can be 6 andplatform 10 as a unit into and out of operative position relative to amarine or air craft. It will be noted that the hinge connection is ofsimple construction and assembly and comprises a pair of apertur'ed lugs21 provided at opposite sides of stairway 2b in an arrangementpermitting the apertures in the lugs aligned with a pair of aperturesprovided in opposite corner posts 8, such alignment permitting the readyrethe like to facilitate ception of removable hinge pins or bolts 19.Thus it will, be appreciated that the stairway 20 can be readily deforrepair, storage tached from the supporting structure 6 or otherpurposes.

In accordance with this invention the stairway 20 may,

optionally, be floatingly or yieldably held in the elevated or guardposition shown by the dotted outline 36 in Fig. 1 to that position whenreor placed in the depressed the full lines in Fig. 1

and automatically returnable lieved of the weight of the user, orlowered position shown by depending upon whether the gangplank is beingused sporadically at night when rodents would be moving about or isbeing used during the night that rodents would not be tempted to makeuse of gangplanh further comprises a manually manipulative connected atone end to the supporting structure 6 and at the opposite end to thestairway 20.

In the preferred embodiment thereof the spring device comprises acylindrical spring housing 14 provided with an integral lug 15 and pivotpin 13..through the medium of which the spring housing is pivotallymounted on one of the cross members 9 of the supporting structure 6.Mounted in housing 14 is a helical spring 16 which has one end suitablyanchored by eye bolt 17 to the housings closed end (see Fig. 3).

Suitably mounted on one of the sidewalls 23 of the stairway 20, as bybeing bolted or otherwise secured thereto as at 11 is a tubular guide 24of a crank assembly. Gudgeoned into the apertured lower end of the guide24 is the actuating screw 25 which is restrained from axial move ment bypin 27 (see Fig.4). The upper end ofscrew 25 is journaled in aperturedplug 28 and is surmounted by a handle or crank 29 exteriorly of guide 24and convenient to a person using the stairway 20 as will be readilyappreciated upon reference to Figs. 1 and 4 of the drawings. i

moved with supporting structure 21 to be readily day or so frequently atspring device which is gudgeon or necked down portion 26 of i at thefree end of spring housing 14. One end of the tie rod 18 is pivotallyconnected to the free end of spring 16 and has its other end affixed toa yoke 35 which straddles nut 30 and trunnioned thereto by two studtrunnions 31. The yoke equipped end of tie rod 18 is accommodated bylongitudinal opening 33 provided in tubular guide 24 as shown in Figs. 4and 5.

The location of the uppermost and lowermost adjustments of the link 18attached to the spring 16 will be determined, in the fabrication of anyspecific gangplank,

by a consideration of the turning moment values which will be createdabout the pivot point 19 of the stairway or walkway. The spring 16exerts a force which acts at a variable distance from the pivot point19. The algebraic value of this variable distance (positive or negative)will determine the turning moment which this force creates. Anadjustment of the position of the yoke end '35 of the link 18 varies thelength of this variable distance between the pivot 19 and the line ofaction of the force I of the spring, thereby changing the turning momentcaused by this force. In every instance, the uppermost adjust mentposition of the link 18 will always be above the pivot point of thewalkway. But the lowermost adjustment position of the link 18 willdepend upon the turning moment which must be counterbalanced, i. e. theweight of the walkway and the distance of the center of gravity of thewalkway from the pivot point. Algebraically, the perpendicular distancefrom the pivot point 19 of the walkway to the link 18 in its lowestposition of adjustment must be less than the product of the weight ofthe walkway 20 and the distance from the pivot 19 to the center ofgravity of the walkway 20 divided by the force exerted by the spring 16in that position. This means that as long as the link 18 in its lowestposition is below the pivot 19, or through the pivot axis, or above thepivot not over a predetermined distance, the weight of the walkway 20will always be sufficient to exceed any counterbalancing action of thespring, and the walkway will remain down. Therefore, the lower positionof adjustment of the link 18 need not necessarily be below the pivotpoint 19 of the walkway 20, as long as the limitations described aboveare satisfied.

In operation, the gangplank is moved into place alongside the passagewayof a water or air craft so that the platform is adjacent thereto. Duringthe day and during periods of frequent use the stairway is normally leftdown since the rodents will remain in hiding during these periods andthere is little danger of their using the gangplank as a means ofingress. However, at night when the gangplank is used only occasionally,it provides a ready help for rodents desiring to enter the craft so thestairway must be kept in the raised or guard position.

From the depressed position, the stairway 20 is raised by turning crank29 and thereby elevating non-rotatably mounted nut 30 which carriestherealong tie rod 18 followed by pivoted housing 14 and spring 16. Asthe 1 tie rod 18 is elevated, the tension of spring 16 comes into playto an increasingly greater extent until it overcomes the weight ofstairway 20 causing it to pivot to a horizontal guard position where itrests against a stop means (not,

shown) mounted on supporting structure 6.

The ladder assembly is fioatingly held in the elevated position solelybythe tension of the spring 16 so when a person leaving the craft comesonto steps 22, the added weight will overcome the force of the springand cause the stairway 20 to be depressed to the ground. When the personsteps off of the steps 22 onto the ground the stairway will be springbiased back to the guard position. Likewise, when a party boards theship or air craft the stairway 20 is first pulled down by hand and afterthe partys ascension will automatically return to the elevated position.

When it is desired to keep the steps lowered, crank 29 is rotated so asto move tie rod 18 down until the weight of the stairway 2t exceeds thedecreasing effect of the tension exerted by spring 16, at which time thestairway will descend to the ground. If tie rod 18 is lowered to a pointwhere it is below pivot 19 as seen in Fig. 1, the force of the spring 16will apply a force tending to hold down the stairway 20 over and beyondthe holding down force of such stairways own weight.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. In a gangplank including a platform and a vertically swingingstairway, a device operable to either normally retain the stairway in anelevated position and automatically return the stairwayto said positionsubsequent to a lowering of the stairway or, optionally, to secure thestairway in lowered position, comprising a spring pivotally anchored tothe platform, a guide member mounted on the stairway substantiallytransverse to the longitudinal axis of the spring, upper and lower endsof said guide member being respectively above and below the pivot of thestairway, a nut mounted in the guide member and constrained to movelongitudinally thereof, a handle equipped screw journaled in the guideand threadedly engaged with the nut to cause the latter to move ineither of two directions in the guide, and a link connection betweensaid spring and said nut.

2. In a gangplank including a platform, a vertically swinging stairwaypivoted to said platform, a device operable to either normally retainthe stairway in an elevated position and automatically return thestairway to said position subsequent to a lowering of the stairway or,optionally, to secure the stairway in lowered position, comprising aspring pivotally anchored to the platform, a guide member mounted on thestairway in transverse relationship to the longitudinal centerline ofsaid spring, upper and lower ends of said guide member beingrespectively above and below the pivot point of the stairway, a nutmounted in the guide member and constrained to move longitudinallythereof, a link connection between said spring and said nut, and ahandle equipped screw journaled in the guide and threadedly engaged withthe nut to cause the latter to move in either of two directions in theguide so as to move the link connection optionally clockwise orcounterclockwise in relation to the pivot between the stairway and theplatform.

3. A gangplank comprising a platform, a vertically swinging walkwaypivoted intermediate its ends at a pivot point tosaid platform, theweight of said walkway causing a turning moment about said walkway pivotpoint, spring means pivotally anchored at one end to said platform, apivotal connection between the other end of said spring means and saidwalkway, said spring means also exerting a turning moment about saidwalkway pivot point, adjustable means mounted on said walkway andoperatively connected with said spring means to shift said outer end ofsaid spring means to a selected position of angular adjustment, saidadjustable means being positioned on said walkway substantiallytransverse to the longitudinal axis of said spring means so as tocontrol and selectively vary said turning moment caused by said springmeans to optionally counteract or supplement the turning moment exertedby the weight of the walkway about said walkway pivot point so as toretain the walkway in either raised, intermediate or lowered position.

4. A gangplank comprising a. platform, a vertically swinging walkwaypivoted intermediate its ends to said platform, spring means pivotallyanchored at one end to said platform, a pivotal connection between theother end of said spring meansand said walkway, adjustable means mountedon said walkway and operatively connected with said spring means toshift said pivotal connection of said other end of said spring meansalong the length of said Walkway, said adjustable means comprising aninternally threaded slidable nut integral with said pivotal connection,a mating screw mounted substantially transverse to the longitudinal axisof said spring means and rotatably secured through bearings to saidwalkway and engaging said slidable nut to shift it as aforesaid alongtne length of said walkway to upper and lower limits of adjustment, saidnut at its uppermost limit of adjustment being located higher than thepivot point between said platform and said hinged walkway, and said nutat its lowermost limit of adjustment being so positioned that theturning moment exerted by said spring means around the walkway pivot isless than the turning moment caused by the weight of the walkway aroundsaid walkway pivot.

5. A gangplank comprising a platform, a vertically swinging walkwaypivoted intermediate its ends at a pivot point to said platform, theweight of said walkway causing a turning moment about said walkway pivotpoint, spring means pivotally anchored at one end to said platform, apivotal connection between the other end of said spring means and saidwalkway, said spring means also exerting a turning moment about saidwalkway pivot point, adjustable means mounted on said walkway andoperatively connected with said spring means to shift said pivotalconnection of said other end of said spring means along the length ofsaid walkway so as to control and selectively vary said turning momentcaused by said spring means to optionally counteract or supplement theturning moment exerted by the weight of the walkway about said walkwaypivot point so as to retain the walkway in either raised, intermediateor lowered position, said spring means including a spring pivoted at oneend to said platform, a link and yoke member joining the outer end ofsaid spring to said pivotal connection between said spring and saidwalkway to control and selectively vary the turning moment caused bysaid spring means comprising an internally threaded slidable memberjoined to said yoke member at said pivotal connection, a support andguide member for guiding said internally threaded slidable member,bearing means fixing said support and guide member to said walkway in aposition substantially transverse to the longitudinal axis of saidspring, an externally threaded member operatively mounted within saidbearing means and engaging said internally threaded slidable member toshift said slidable member along said support and guide member, andcrank means to axially rotate said externally threaded member.

6. A gangplank comprising a platform, a vertically swinging walkwaypivoted intermediate its ends at a pivot point to said platform, theweight of said walkway causing a turning moment about said walkway pivotpoint, spring means pivotally anchored at one end to said platform, apivotal connection between the other end of said spring means and saidwalkway, said spring means also exerting a turning moment about saidwalkway pivot point, adjustable means mounted on said walkway andoperatively connected with said spring means to shift said pivotalconnection of said other end of said spring means along the length ofsaid walkway so as to control and selectively vary said turning momentcaused by said spring means to optionally counteract or supplement theturning moment exerted by the weight of the walkway about said walkwaypivot point so as to retain the walkway in either raised, intermediateor lowered position; the adjustable means to shift said pivotalconnection along the length of said walkway comprising an internallythreaded slidable nut integral with said pivotal connection, a screwmating with said nut mounted substantially transverse to thelongitudinal axis of said spring means and rotatably secured throughbearings to said walkway and engaging said slidable nut to shift it asaforesaid along the length of said walkway to upper and lower limits ofadjustment, said nut at its uppermost limit of adjustment being locatedhigher than the pivot point hinging said platform and said walkway,whereby said turning moment exerted by said spring means around saidwalkway pivot point counteracts and exceeds the turning moment exertedby the weight of said walkway, and said nut at its lowermost limit ofadjustment being so positioned that the turning moment exerted by saidspring means around said walkway pivot point then supplements theturning moment exerted by the weight of said walkway.

References Cited in the file of this patent UNITED STATES PATENTS228,779 Perkins June 15, 1880 1,379,836 Rackham May 31, 1921 1,836,453De Veau Dec. 15, 1931 1,992,099 Smith Feb. l9, 1935 2,233,638 Peck Mar.4, 1941 2,399,150 Snider Apr. 23, 1946 2,549,140 Svendsen Apr. 17, 19512,617,131 Harris Nov. 11, 1952

